In a known thermocouple, a first end of each of two kinds of metal wires, for example, alumel and chromel, are connected to one another. The thermocouple measures the thermoelectromotive force occurring between two opposite second ends. Interposition of a different kind of metal, such as copper, between the second ends and a measuring device causes a measurement error. Known thermocouples thus use an alumel lead wire to connect the alumel wire to the measuring device, and a chromel lead wire to connect the chromel wire to the measuring device.
Japanese Patent Application Laid-Open No. 2002-26399 (“JP 2002-26399”) and Japanese Utility Model Application Laid-Open No. H05-6720 (“JP H05-6720”) both disclose connectors connecting a compensating lead wire made of the same kind of metal to a metal wire constituting a thermocouple. JP 2002-26399 discloses a thermocouple connector having a pin-side connector with an electrode pin biased by a coil spring and an end face-side connector having an electrode end face. However, in JP 2002-26399, in order to maintain connection between the pin-side connector and the end face-side connector, a lock mechanism is additionally required, and the structure of the connector is complicated to manufacture. JP H05-6720 discloses a thermocouple connector having a plug terminal and a socket terminal with a flat spring member including a bimetal structure. A contact pressure between the plug terminal and the socket terminal may fluctuate with temperature, causing a measurement error. Further, some metals used for thermocouples, such as alumel, chromel, or constantan, have poor ductility, malleability, or elasticity, and are unsuitable in themselves as electrical terminal materials.